Method of manufacturing a trimmer potentiometer

ABSTRACT

Apparatus and method of manufacturing a trimmer potentiometer including a nonconductive substrate. A conductive track is deposited on a first surface of the substrate. Resistance material is also deposited on the surface of the substrate to form a resistance path. Nonsolderable material is deposited on selected portions of the conductive track to form dam sections thereon. Terminal pins are soldered to the ends of the conductive track, the dam sections restricting the flow of solder along the conductive track to essentially the end portions thereof.

United States Patent [191 [1 3,913,222 Bernard Oct. 21, 1975 [54] METHOD OF MANUFACTURING A 3,610,811 10/1971 OKeefe 29/490 X TRIMMER POTENTIOMETER gelriingler et al. Q

, a QC [75] Inventor: Russell J. Bernard, La Habra, Calif.

[73] Assignee: Spectrol Electronics Corporation, Primary Examiner-Victor A. DiPalma City of Industry, Calif. Attorney, Agent, or Firm.l. Raymond Curtin; Barry 22 Filed: May 13, 1974 Deutsch [21] Appl. N0.: 469,195 [57] ABSTRACT p Apparatus and method of manufacturing a trimmer [52] US. Cl. 29/621, 29/490,32398//537289, potentiometer incuding a nonconductive Substrate A [51] Int C12 H01 C 17/28 conductive track is deposited on a first surface of the [58] d 578 589 substrate. Resistance material is also deposited on the le 0 338/329" 7 surface of the substrate to form a resistance path.

Nonsolderable material is deposited on selected por- [56] R f d tions of the conductive track to form dam sections e erences l e thereon. Terminal pins are soldered to the ends of the UNITED STATES PATENTS conductive track, the dam sections restricting the flow 2,904,772 9/1959 Artz 29/490 X of solder along the conductive track to essentially the 3,268,653 8/1966 MCNUH 29/490 X end portions thereof 3,386,165 6/1968 Bruhl, Jr. et a1 29/621 3,601,889 8/1971 Kaneoya 29/621 X 6 Claims, 5 Drawing Figures we I 1. METHOD OF MANUFACTURING A TRIMMER POTENTIOMETER BACKGROUND OF THE INVENTION This invention relates to trimmer potentiometers, and in particular, to a novel apparatus and method of manufacturing same.

Trimmer potentiometers-of varied designs and configurationsare employed throughout society. Many of such trimmer potentiometers include a nonconductive substrate on which both the materials defining the resistancepath and the conductive path -are.deposited. The wiper or contact element is moved along the resistance path so that desired resistance values or; voltage ratios may be obtained in the circuit employing the trimmer potentiometer. Typically, the terminal pins are soldered or otherwise affixed to end portions of the conductive path.

In many potentiometer designs employing nonconductive substrates,.the substrate is utilized-toclose off one end of the potentiometer housing..Epoxy,- or a similar adhesive, is then deposited about thesubstra,te to firmly affix the substrate relative to the housing. In many such designs, the surface of the substrate in contact with the housing forms a seal therewith to prevent epoxy material or similar foreign bodies from gaining. access into the interior of-the housing.

It has been found in some cases, solder employed in affixing the terminal pins to the substrate has flowed along the conductive track. As-, a result of this undesirable movement of solder, raised portions are produced on the surface of the substrate to thereby destroy the sealbetween theopposed surfaces of the substrate and housing. Foreign material has thus'gained ingress into theJinterior of the housing, thereby introducing potential sources of problems to ;the"c'on'tinued satisfactory operation of the device. p I

In addition, if thesolder flows substantially along the entire length of the-conductive path, there arises a possibility of the solder moving onto the resistance track. Any solder on the resistance track might result in shorting of portions thereof or in changing the total resistance value thereof.

The present invention finds particular utility with resistance devices using a resistance material which is applied as a layer or film on a nonconductive support or base. A suitable resistance material that has found widespread acceptance in the industry is formed of a mixture of glass and metal particles and is commonly called cermet resistance material.

SUMMARY OF THE INVENTION It is therefore an object of this invention to manufacture trimmer potentiometers including substrates wherein opposed surfaces of the substrate and housing maintain an effective seal therebetween.

It is a further object of this invention to manufacture trimmer potentiometers of high quality.

It is another object of this invention to manufacture trimmer potentiometers wherein solder employed in affixing the terminals to the conductive path is maintained at desired predetermined locations.

It is a further object of the invention to manufacture high quality trimmer potentiometers without increasing the cost thereof.

It is still another object of the invention to form a trimmer potentiometer substrate of unique design.

The present invention relatestoapparatus and manufacture of trimmer potentiometers, including a nonconductive, substrate, comprising the steps of depositing material to form aconductive track on a first surface of thesubstrate. Resistance material is deposited on the surface of the substrate to form a resistance path. Nonsolderable material is deposited on selected portions of the conductive track to form dam sections thereon. Terminal pins are soldered to the ends of the conductive track, the dam sections limiting the flow of solder to predetermined portions thereof.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a plan view of a substrate employed in trimmer potentiometers manufactured in accordance with the'present invention;

FIG. 2 is a view of the substrate after processing;

FIG. 3 is a sectional view of the substrate taken along lines IIIIII of FIG. 2;

FIG. 4 is a view of the substrate after further processing; and

FIG. 5 is a sectional view of the substrate taken along lines VV of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is illustrated a nonconductive substrate employed in trimmer potentio rneters manufactured in accordance with the present invention. The substrate is illustrated during various stages of the manufacturing process.

The substrate 10 is formed from a nonconductive material, for example a ceramic composition. The substrate may be in the form of a circular or rectangular disc or water. Other geometric configurations may-be suitably employed. Substrate 10 has material defining a conductive track or path 11 deposited on a first surface 10 thereof, by suitable means for example either spraying or.screening. Conductive track 11 includes end portions 13, 14 and 15 and a collector portion 12. The conductive material used to form track 11 may. comprise a silver or gold composition. The configuration of the conductive track may be suitably modified to meet the requirements of particular applications.

Material defining a resistance track 16 is also deposited on surface 10' of substrate 10. The resistance material may comprise either a cermet composition or a carbon composition, both types of resistance materials being well-known to those skilled in the art. The resistance material may either be sprayed, screened, brushed or stenciled onto the surface of the substrate.

The resistance material is applied to the base in a configuration desired for the particular application of the resistance device. In the present embodiment, the resistance material is placed on the substrate in a substantially annular or arc-shaped pattern. Those areas on the surface of the substrate upon which it is not desired to deposit any material, are masked via suitable means.

Additionally, nonsolderable material, for example the same material comprising the resistance material is deposited at predetermined portions of the conductive track. Such additional nonsolderable material 17, 18 and 19 extends above the surfaces of the substrate and of the conductive track.

In order to provide the additional material l7, l8 and 19 without increasing the cost of manufacturing trimmer potentiometers, it is preferable to deposit the additional material l7, l8 and 19 simultaneously with the deposition of the resistance material forming the resistance track or path. The simultaneous deposition of the resistance material forming track 16 and additional material 17, 18 and 19, may readily be accomplished by using a screening process.

Subsequently, terminal pins 20, 23, and 24 are affixed to end portions l3, l4 and 15 of the conductive path. Typically, the terminals are affixed to the conductive path via solder, illustrated at points 22, 25 and 27.

Generally, the opposed surfaces of substrate and of the potentiometer housing are placed into engagement to define a seal. The seal prevents foreign matter, such as epoxy used to affix the element to the housing, from gaining ingress into the housing. Heretofore, it has been possible for solder to flow along the conductive path to thereby form raised areas on the surface 10 of substrate 10 to prevent a proper seal from being obtained.

Additionally, solder might adhere to the contact member of the resistance device to thereafter be deposited onto the surface of resistance path 16, to thereby either change the resistance value of the path or to provide shorting areas thereon.

To obviate the foregoing problems, additional nonsolderable material l7, l8 and 19 has been placed at predetermined portions of the conductive path to restrict the flow of solder. In essence, the additional material l7, l8 and 19 functions as dams to prevent the solder from flowing from the end portions of the conductive path where the solder is initially deposited.

The utilization of dams effectively maintains the solder at the end portions l3, l4 and of conductive path 11. The elimination of problems associated with undesirable solder flow may thus be accomplished without significantly increasing the cost of manufacturing such devices.

While a preferred embodiment of the present invention has been described and illustrated, the invention should not be limited thereto, but may be otherwise embodied within the scope of the following claims.

lclaim: I I I. In the method of manufacturing a trimmer potentiometer, including a nonconductive substrate, wherein a conductive track'is deposited on a first surface of the substrate, resistance material is deposited onthe surface of thesubstrate to form a resistance path, and terminal pins are soldered to the ends of the conductive track, .the improvement comprising? I depositing an additional quantity of resistance material on selected portions of the conductive track to form dam sections functioning to limit the flow of solder along the conductive track to predetermined sections thereof.

2. A method of manufacturing a trimmer potentiometer, including a nonconductive substrate, comprising the steps of:

depositing a conductive track on a first surface of the substrate; g depositing resistance material on the surface of the substrate toform a resistance path;

depositing nonsolderable material on selected portions of the conductive track to form dam sections thereon, the deposition of said nonsolderable material occurring simultaneously with the deposition of said resistance material; and

soldering terminal pins to the ends of the conductive track, the dam sections limiting the flow of solder along the conductive track to predetermined portions thereof.

3. A method in accordance with claim I wherein the resistance material is a cermet composition. I

4. A method in accordance -'with claim 3 wherein the deposition of said resistance material is accomplished via a screening process.

5. A method in accordance with claim- 2 wherein the resistance material is a cermet composition.

6. A method in accordance with claims wherein the deposition of said resistance material and said-nonsolderable material is accomplished via a screening pro-- CCSS. 

1. In the method of manufacturing a trimmer potentiometer, including a nonconductive substrate, wherein a conductive track is deposited on a first surface of the substrate, resistance material is deposited on the surface of the substrate to form a resistance path, and terminal pins are soldered to the ends of the conductive track, the improvement comprising: depositing an additional quantity of resistance material on selected portions of the conductive track to form dam sections functioning to limit the flow of solder along the conductive track to predetermined sections thereof.
 2. A method of manufacturing a trimmer potentiometer, including a nonconductive substrate, comprising the steps of: depositing a conductive track on a first surface of the substrate; depositing resistance material on the surface of the substrate to form a resistance path; depositing nonsolderable material on selected portions of the conductive track to form dam sections thereon, the deposition of said nonsolderable material occurring simultaneously with the deposition of said resistance material; and soldering terminal pins to the ends of the conductive track, the dam sections limiting the flow of solder along the conductive track to predetermined portions thereof.
 3. A method in accordance with claim 1 wherein the resistance material is a cermet composition.
 4. A method in accordance with claim 3 wherein the deposition of said resistance material is accomplished via a screening process.
 5. A method in accordance with claim 2 wherein the resistance material is a cermet composition.
 6. A method in accordance with claim 5 wherein the deposition of said resistance material and said nonsolderable material is accomplished via a screening process. 